When Beaver County, Utah Territory was created 5 January 1856[1][2][3] from the southern part of Millard and northern part of Iron counties, Beaver County extended into present-day Nevada from Utah Territory's eastern boundary to the western edge of the Carson County between Milliard and Iron counties in Utah Territory.

Utah Territory's old 1856 counties are named in orange. Present-day Nevada counties are outlined in white.

In 1861 the U.S. Congress created Nevada Territory with its eastern border at 116° W, and in 1862 moved Nevada's eastern border one degree of longitude east, and repeated that again in 1866, each time reducing Beaver County, Utah.[4] Former Beaver County land in present-day Nevada was used eventually to form parts of Mineral, Esmeralda, Nye, and Lincoln, counties.[5]

For records of the old Beaver County in what is present-day Nevada, see: